1. Field of the Invention
This invention relates to an improved process for producing ionically crosslinked copolymers.
2. Description of the Prior Art
U.S. Pat. No. 3,404,134 discloses a process for ionically crosslinking copolymers of carboxylic acids and alpha-olefins, i.e., neutralizing some of the carboxylic acid groups with metallic cation-supplying material. If the metallic cation-supplying material is substantially insoluble under the reaction conditions, it is desirable to convert the insoluble material into a soluble one in situ to accelerate the reaction. This may be accomplished in the case of metal oxides, hydroxides and carbonates by the addition of acid such as acetic acid.
U.S. Pat. No. 3,649,578 discloses an improved method for producing ionically crosslinked copolymers. The copolymers had improved properties such as less residual water from the process; did not have obnoxious odors which were present when the water-insoluble cation-supplying material was rendered water-soluble by the use of agents such as acetic acid and did not contain white specks. While the ionically crosslinked copolymers were of good quality, as the production rate increased it was found necessary to activate the cation-supplying blend either with water or acetic acid. Frequently, even though an activator was used, unreacted metal salts such as zinc oxide could be observed in the final product.